Moving object tracking systems that pick up a movement of a tracking subject such as a person or an object as a moving image using a surveillance camera and determine a movement of the picked up person or object by analyzing the moving image have heretofore been provided. The moving object tracking system is usable for traffic control, vehicle travel assistance, and the like by determining movements of vehicles, for example. Also, the moving object tracking system is usable for passersby status investigation, customer behavior investigation, and the like by determining movements of passersby in public areas and movements of customers and the like in retail premises. Also, the moving object tracking system is usable for production control, production planning, and the like by determining movements of production subjects in a production line in a plant and movements of workers.
Such moving object tracking system is provided with an image processing apparatus for performing an image processing on picked-up images which have been picked up by the surveillance camera. Such image processing apparatus detects movements of a detection subject by performing a processing of associating the detection subject in a current image (reference image) to the detection subject in a past image (reference image) as an identical object.
In the association processing, a region including an entire image region of the detection subject is set as a correlation window based on the reference image. By performing a search in the reference image with the use of the correlation window, a position of the correlation window at which a difference between pixel values in the correlation window in the standard image and pixel values in the correlation window in the reference image is minimized is determined as a position of the detection subject in the reference image.    [Patent Publication] JP-A-2003-346159 (published on Dec. 5, 2003).